Sealing cement block foundations as another barrier against water intrusion with Dry lok
The second issue to address is to seal the porous cement block so that you have an effective barrier against water intrusion. I used a product called DRYLOK to seal the walls in my basement. You may also see it spelled as Drylock and Dryloc elsewhere on the internet. Drylok is a paint/sealant that forms a strong barrier against moisture and can be used on cement block. I was told to put it on as if I stole it - that is - apply it very liberally. My professional basement remodeler, Jerry Newkirk, recommends up to five coats of drylok for new/never sealed basement walls and fewer coats for basement walls that have been sealed in the past. He recommends reapplying drylok every two years. The results obtained from drylok were nothing short of phenomenal. My basement went from summertime humidity readings of sometimes close to 100% (where the walls would be wet to the touch - before drylok) to an average of about 60% humidity (after drylok application) with occasional hi readings of 75% on really muggy days without use of air conditioning. The damp, musty smell disappeared completely after Drylok application, and the entire basement can now be used much as the rest of the house. I have a living room set up now as well as an office space. Drylok application also eliminated most of the mold issues in the basement as much of the water penetration has been taken care of. In the photo to the left, you'll see the condition of the basement walls as they were prepped for drylok application. Care should be taken to scrape all loose paint/sealant from the walls and to remove dirt, dust and mold accumulations.
I've noticed that many people who have come to this site wonder if drylok will also make a basement feel warmer or seal out the cold air. That's a good question. To a certain extent, drylok does act as a small form of insulation. My buddy swore that my basement was a lot warmer after the drylok application. It may be a litte warmer and drylok may help in that regard. But I don't think that it has made a huge difference.
March 20, 2007 - It's been one year since I finished the main room in my basement using Dry lok as the foundation for a dry basement. The dry-lok finish on the cement block walls is still holding strong and has proved to be a strong barrier against water intrusion. I've notice some efflorescence forming in spots but no big deal. Overall dry lok has done its job in wet and humid central Ohio.
A couple other concerns that people have asked about our making a basement airtight and heating a basement. I used a product called "Great Stuff" to fill in cracks and holes in the foundation walls. Great Stuff is an expanding foam that insulates. Don't breathe in the vapors though. It's pretty noxious. That's a good start at making your basement airtight. Also check the insulation near the ceilings. As far as heating a basement, basements will always be cold as they are underground and you are usually right on top of a cement slab. Carpeting helps as do portable heaters. I have a fireplace in my basement and would like to add a gas insert for extra heat.